Ultrasonic apparatus and method for analyzing defects in material

ABSTRACT

A pair of ultrasonic transducers, operatively connected to electrical signal generating and detecting circuits, are mounted in spaced relationship for movement through a liquid confined in a couplent chamber. A flexible wall of the chamber is adapted for close engagement against a wall surface of material to be tested for a suspected internal flaw. The chamber can be selectively positioned on this surface for ultrasonic energy transmission through the flexible wall into the material at a plurality of positions adjacent the suspected defect. A series of passes of the transducers is made in sequential order along lines longitudinally oriented with respect to the surface but transversely spaced across the surface. At those points where the detecting means reveal an interruption, or resumption, of ultrasonic energy transmission through the material, scale indicators, associated with the transducers, can be read to obtain numerical values indicative of the profile and location of the suspected defect.

Unie tate Stearns FOR ANALYZING DEFECTS IN MATERIAL Oct. 30, 1973Primary Examiner-Richard C. Queisser Assistant Examiner-Arthur E.Korkosz Attorney-Robert S. Auten et al.

[76] Inventor: Charles A. Stearns, Apt. 17, 2215 Ambassador Dr., NE.Executive West, Albuquerque, N. Mex. 87100 [57] ABSTRACT 22 Filed- Dec20 3971 A E LMQLHlHQ -QQIQnli la srdl i fsi Operatively nected toelectrical signal generating and detecting [2]] Appl. No.: 209,870circuits, are mounted in spaced relationship for movement through aliquid confined in a couplent chamber. A flexible wall of the chamber isadapted for close enfiltSbCll g g against a wall Surface of material tobe i 67 7 67 8 tested for a suspected internal flaw. The chamber can abe selectively positioned on this surface for ultrasonic energytransmission through the flexible wall into the i I material at aplurality of positions adjacent the sus- [56] (defences-Cited pecteddefect. A series of passes of the transducers is UNITED STATES PATENTSmade in sequential order along lines longitudinally ori- 2,971,3722/l96l Lewis et al 73/675 R ented with respect to the surface buttransversely 3,426.585 2/1969 Zemanekft film 73/67-7 spaced across thesurface. At those points where the 2,846,875 8/1958 Grabendorfe' 73/67-8detecting means reveal an interruption, or resumption, of ultrasonicenergy transmission through the material, 2799l57 7/1957 gn 73/67 7scale indicators, associated with the transducers, can be read to obtainnumerical values indicative of the profile and location of the suspecteddefect.

7 Claims, 13 Drawing Figures 84 1, (TRIGGER -3 WED s 85 REF? RATE GATE 0CILLOSCOPE GENERATOR OUTPUT TRANSMITTER ,tt, 30 a RECIEVER 86 SELECTOR72' 74 SWITCH l3 CRYSTAL "a" 55 |7 r t- *1 Z28? S 1 j 87 87' SPECIMEN tPMENTED B 30 19 v 1 ,769,308

SHEU 10F 6,

PAIENIEDnm 30 ms SHEET 2 OF 6 4m QE 3 M E PATENTED BC! 30 I975 SHEET 5OF 6 ULTRASONIC APPARATUS AND METHOD FOR ANALYZING DEFECTS IN MATERIALBACKGROUND OF THE INVENTION The invention relates in general toultrasonic testing of materials. The determination of properties of amaterial by measuring the transmission of ultrasonic waves through thematerial is now well known in the art. In fact various types ofapparatus and methods have been devised to use ultrasonic waves as thetesting medium in a number of fields.

One of the most promising fields for the use of apparatus and methodsdesigned for ultrasonic testing of material is in the testing ofrailroad track rails to determine whetehr flaws or defectsexist in therail or in the welds between rail sections. Obviously a defective railor a weld can present a real hazard to train operation and this hazardis of increasing concern as train speeds and weight are increased tomeet modern operating conditions. i

In order to detect flaws of defects in railroad track,

rail flaw detector cars, which can move on the rails in the track, havebeen used for some time. Various systems have been used including theuse of ultrasonic equipment in which the ultrasonic energy istransmitted into the rail by means of transducers that are operativecoupled to the rail by means of a couplent such as water or oil. Withthis arrangement ultrasonic waves can be transmitted into the rail asthe car moves along the track and during such movement indicating meanson the car are scruitinized and the indications analyzed lar ultrasonictrajectory (mean, about 27 from the horizontal) most of the wave energycourses at or near the surface of the rail. While penetration in depthis more than adequate, typical defects of moderate size, having an upperlimb more than approximately one tenth of an inch beneath the surface ofthe rail cannot be detected at distances greater than 4 or 5 inches,however strong the transmitted signal energy. One the other hand deepheadchecking, thermal cracks and certain shelling may present an idealtarget, since there is virtually no resistance to energy conducted at ornear the surface of the rail. Furthermore, these defects may be detectedat a distance six times that of the legitimate defect of moderate size.In addition the echoed signal, since it is collected after considerabledispersion, several inches from the target, cannot indicate the size ofthe target, but only its reflective quality. Therefore it is oftenimpossible to distinguish between small, but important defects andhighly reflective, insubstantial surfaces, such as are presented bydendritic crystallization in welds, the improperly ground fillets ofcertain welds, and certain shelling and headchecking.

Because of the above mentioned problem it is necessary in some cases tostop the car and to make an on the spot check of suspected defects whichmight be indicated by the car equipment. In the art this is known ashand-testing and of course permits a more precise and efficientdetermination because the equipment is used to scan a very restrictedarea of rail. This hand check then permits a more accurate testing thanis generally obtainable in the use of flaw detector cars. ln fact,hand-testing is often required at specific locations along the track atwhich it may be difficult for the flaw detecting equipment on the car toadequately and accurately detect the flaw or the defect.

However pulse-echo ultrasonic hand-test devices presently used to verifydefects found by ultrasonic detector cars cannot readily differentiatebetween insignificant small cracks with highly reflective facets, andtrue developed defects which present, by virtue of their irregularities,a surface of inferior reflectivity. This problem exists also in testingof materials and welds in fields other than that of track testing.

SUMMARY OF THE INVENTION It is therefore an object of the invention toprovide apparatus which can be used to accurately indicate size, shapeand position of defects or flaws in a material and thereby provide ameans for differentiating between such defects or flaws. I It is afurther object of the invention to provide a portable apparatus whichutilizes ultrasonic test means which can be applied to a single surfaceof a material to be scanned for internal defects or flaws.

.While the system and apparaus, according to the invention, will bedescribed later in conjunction with its use in testing of railroad railit should be stressed that this is only one field of testing in whichthe invention can be advantageously used. Thus the invention can be usedfor testing welds in many areas such as in pipe lines, hulls ofsubmarines and other ships, building structures, or welded piecesconveyed on assembly lines adaptable to jigging for testing purposes.

In general the apparatus provided to carry out the analysis of defectsin material includes a couplant chamber which can be adjustablypositioned on the material, such as a railroad rail, over a suspecteddefect area or an area to be initially tested. A bottom wall of thechamber is flexible so as to closely conform to and make close contactwith the surface contour of the material. The couplant chamber alsoserves to support a carriage which is movable over the couplant topsurface'flfiin'gitridiriallylwithj respectto the surface of the -maerial. This carriage carries two ultrasonic transducerholdEs'vi hichdeperid'fromthe carriage to position the transducers in a couplant inthe chamber and thgmtransducers are adjustable with respect to thesurface of the material. The l olders ar e lgrrgitudinally the carriageand this spacing between big-Egan m,

Suitable ultrasonic excitation and receiving means are provided wherebya transmitting transducer, in the form of a piezoelectric crystal,transmits an ultrasonic wave into the rail and this wave travels throughthe rail and is reflected from a surface thereof to be received at thereceiving crystal connected to suitable signal re- .ceiving andindicating means. The angle of transmission of the ultrasonic waves intothe head of the rail on which the apparatus is positioned can be variedto suit conditions existing at the spot and in operation the defect orflaw which is to be analyzed is traversed bylhg carriag efiic arryingthe transmitting and receiving transducers.

Before commencing the operation, the generallocation of the flaw isdetermined and the couplant chamber is disposed centrally over this flawarea. The carriage containing the transmitting and receiving crystals,spaced apart at a predetermined distance, is positioned to one side ofthe flaw. Further, the carriage is positioned at a first location sothat the transmitting and receiving crystals are transversely spacedfrom an edge of the rail, say the gauge side. This position defines afirst plane or line for one pass of the transmitting and receivingcrystals longitudinally of the rail. Once this position has been set thecarriage is moved say from left to right across the defect or flaw. In apoint-to-point transmission ultrasonic energy is transmitted into therail and is received at the' receiving crystal as the beam is reflectedfrom a rail surface such as the bottom of the rail head or the filletportion thereof. On either side of the defect this transmission iscontinuously. received and the crystal indicating means will indicate acoritinii ity of wave transmission. However, as the flaw is appreachedthe gasqnjssraystraine and there islginterruption,orattenuation ofti'IQgHggS- mission of ...ES..E9 i m the apparatus is moving acro tion.Dependent upon the size (Einsmission will be completed after a meinterval when the apparatus has passed beyond the flaw and at that time,the indicating means will indicate this reemergence of the ultrasonicwave transmission previously blocked by the flaw.

At the times that the indicating means reveal an interruption orresumption of ultrasonic energy transmission a marker arm is moved tothe position then occupied by the receiving crystal as longitudinallyspaced from the defect. A scale means associated with the marker arm isthen read to determine the depth within the material, of the upper andlower limbs or surfaces respectively of the defect.

After the above described movement of the carriage in one direction thecarriage is then moved from right to left and the location of thecrystals at the time of wave attenuation is again noted. Thus four fixesare obtained on the flaw; two from the cut-off point or interruption ofwave transmission and two at the point of resumption or emergence ofwave transmission. The pairs of fixes can then be averaged to give thedesired measurement of the upper and lower limbs of the flaw.

If itis desired to corroborate measurements taken in the mannerdescribed above, the distance between the transmitting and receivingcrystals can be changed so there will be a new angle of transmission ofultrasonic energy between the crystals. The operation just described isrepeated to give new fixes on the flaw or defect.

It will be appreciated that passes made along one plane or line,generally longitudinally oriented with respect to surface of thematerial being tested, will give no clue as to the transverse extent ofsuch flaw or defeet. In order to obtain this profile the couplentchamber can be displaced transversely from the first plane to a secondplane or line where measurements can again be made in a similar manner.The couplent chamber can then be moved to'a third plane and, ifrequired, to successive planes until the transverse dimension of theflaw is measured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of theanalyzer as positioned on top of a piece of material which is to-betested.

FIGS. 2a and 2b together show a top plan view of the analyzer.

FIGS. 3a and 3b together show a front elevation view of the analyzer.

FIG. 4 is an end view of the analyzer.

FIG. 5 is a detailed view of the mounting means for :a crystal holdershown partially in section, which is used in the analyzer.

FIG. 6 is a side elevation view of one of the components of the mountingmeans shown in FIG. 5.

FIG. 7 is an end view of another component used in the mounting means.

FIG. 8 is a side elevation view of still another component of themounting means.

FIG. 9 is a diagrammatic disclosure of the electronic system associatedwith the transducers used in the analyzer.

FIG. 10 is an end view of a rail which has a defect on the head portionand showing diagrammatically the scanning lines.

FIG. 11 is a diagram showing the trigonometric functions used inderiving one of the scales used in the analyzer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As seen in FIG. 1 the analyzer,generally shown at 10, includes a body portion and a top wall portion,generally indicated at 11 and 12 respectively. The analyzer is adaptedto be releasably positioned on the surface 13 of a piece of material tobe tested and, for purposes of this disclosure, the analyzer will bediscussed as it is used on a head of railroad rail.

Looking also at FIGS. 2, 3 and 4 it will be seen that body portion 11 isin the form of a relatively long container with side walls 14 and endwalls 15. The lower wall of the body portion is formed with a thinrubber or plasticmembrane 16, which, as best seen in FIG. 4, is designedto closely adapt to the contour of the top surface 13 of the rail head17. The body portion as thus formed is trough-like in shape and isconstructed to contain a liquid couplant, such as oil or water, notshown, for transmitting ultrasonic energy between ultrasonic generatingand receiving means carried in the liquid, in a manner to be describedlater, and the surface of the rail head.

At each end of body portion 11 walls 18 which extend between side wallsl4 define, with end walls 15, chambers, generally indicated at 19, whichare open at the bottom. A permanent magnet 20 is mounted on a shaft 21,extending between walls 15 and 20, for relative pivotal movement withrespect to the chamber 19. At the lower end of each magnet 20 there is arunner 22, with index mark 23, which extends downward through the openbottom of chamber 19 and clamps the body portion 11 to the top surface13 of the rail head'17. As shown in FIG. 1 a knurled knob 24 is securedto each end wall 15 so that the body'portion 11 can be tilted withrespect to the clamping means and another index mark 25 on wall 15 isprovided to give an indication of the extent of angular movement.

As shown in FIGS. 1 and 3 a side wall 14 of body portion 11 has a scalegenerally indicated at 26, with eight inches marked off in bothdirections from a zero point at which there is an index mark 27. Thepurpose of this scale will be discussed later.

The top wall portion 12, which is adapted to be secured to and overliethe body portion 11, is a plate, generally rectangular in shape, whichhas a lip portion 28 that extends transversely away from the bodyportion 11. A groove, generally shown at 29, extends longitudinally ofthe top wall portion 12 in the top surface thereof. Three slits 30, 31and 32 extend downward from the slot through the top wall portion 12 andthe purpose of these slits will be explained later.

A scale, generally indicated at 33, similar to scale 26 is located atthe side of the groove 29 in the top wall portion 12 and is aligned withthe latter scale when the analyzer is assembled. On the opposite side ofthe groove there is a logarithmic and scalar grid shown generally at 34,with the scalar scale, indicated as scale A and logarithmic scale asscale B. It will be observed that from a central pivot point 35, onwhich a marker arm 36 is pivotally mounted, scale A consists of a seriesof spaced parallel lines numbered from 1 to 0 and located on both sidesof the pivot point 35. A series of outwardly diverging guide lines 37extend to both sides from each of the parallel lines. The pivot point 35is aligned with the 0 (zero) marks on both scales 26 and 33.

The logarithmic scale, scale B, consists of a plurality of spaced butparallel lines, numbered 1.0 to 4.0 which are transversely disposed withrelation to the lines of scale A and also cut across the guide lines 37.

The scale B is a logarithmic convergence derived from the spacerelationships shown in FIG. 11 in which AB= Maximum possible separationof transmit and receive crystals 8.0 inches.

s one-half the selected distance between transmit and receive crystals rRatio of distance fromtransmit to receive crystals to AB=CR/AR=s/AR KConvergence factor of A8 to EF== AB/EF=4. QR= c 1.0 inch EQ 1.0 inch RS=Depth or thickness of specimen, herein regarded as unity (1). As seen inFIG. l1

Tan 0 c/(s-s7K) 1/( y/ and x l -(s/K) While 4.0 inches=0.0000" 3.8inChes=0.0l75" 3.6 inches=0.0370" 3.4 inches=0.0588" 3.2 inches=0.G833"3.0 inches=0.l l l l" 2.8 inches=0.l428" 2.6 inches=0.l794" 2.4inches=0.2222" 2.2 inches=0.2727" 2.0 inches=0.3333" 1.8 inches=0.4074"1.6 inches=0.5000" 1.4 incheF=0.6l90" 1.2 inches==0.7777" l.0inches=l.0000" The areas between the lines of scale B can be color codedto facilitate the reading of the scale.

As seen in FIGS. 1 and 2 the marker arm 36 is shown in a rest positionby full lines and in an indicating position by dashed lines. The swingof the arm to one indicating position is shown by the arc segment linewith arrows at both ends. The manner in which these scales are used inconjunction with movement of the arm 36 to engage other elements of theanalyzer will be discussed later.

A sliding carriage 38, shaped to fit in groove 29, can be manually movedlongitudinally of the analyzer 10 by knobs 39 and for ease of movementthe carriage 38 can have a lower surface of teflon. As shown best inFIGS. 1 and 2 carriage 38 has three slits 40, 41 and 42, which arealigned with slits 30, 31 and 32, respectively, when the carriage is inthe groove. Alongside of slit 41 a scale generally indicated at 41' andmarked on the carriage as scale C, has a center point marked l, which asbest seen in FIG. 2 is laid out with inch marking extending from thispoint to 4 inch marks near knobs 39.

Two members for adjustably, supporting crystal holders, to be describedlater, are generally indicated at 43 and 44. These members are ofidentical construction and are slidable on sliding carriage 38. Eachmember includes a top plate 45, shaped for guided movement alongside thescalar and logarithmic scale 34, having at one end spaced dependent arms46 and 47. When members 43 and 44 are in position on sliding carriage 38the arms 46 and 47 extend downward through slits 40 and 42 in carriage38 and aligned slits 30 and 32 in top wall portion 12 so that the lowerportions of these arms lie in the liquid couplent carried in the bodyportion 11.

On the top surface of each too plate 45 there is a projecting log stopmember 48 which is magnetic and is designed to coact with the marker arm36 in a manner to be discussed later. In addition there is a slit 49 ineach top plate and alongside this slit is a scale, generally indicatedat 50, marked from 0 to 30 degrees. Also as shown in FIGS. 1, 3 and 5,each top plate 45 has an index mark 51 on a side face to move over scale33-. A permanent magnet 52 is carried by top plate 45 to adjustablyclamp the crystal holder member along sliding carriage 38. l

As previously mentioned, the construction of members 43 and 44 isidentical and attention is now directed to FIGS. 4-8, inclusive showingmore details of member 43. A pair of stainless steel plate members 53,one of which is shown in FIG. 5, are secured, as by rivets 54, todependent arms 46 and 47 in a manner as best seen in FIG. 5. Each of theplate members 53 has an opening 55 and a circular groove 56, coaxialwith this opening as shown in FIG. 8.

As mounted on the arms 46 and 47, the grooves 56 in the pair of platemembers 53 face each other and a stainless steel tube 57 is received inthe facing grooves to be confined between the plate members. In thismanner tube 57 is mounted to lie below, and transversely disposed, withrespect to top plate 45. As seen in FIG. 6 this tube has oppositelydisposed openings, indicated at 58 and 59, in its wall surface, and thereason for these holes will be explained later.

Rotatably mounted within tube 57 is a stainless steel rod 60, as shownin FIG. 7, and this rod has an axial length approximately equal to theaxial length of tube 57. The rod 60 has an opening 61 extending into theto project from the rod 60, as best seen in FIG. 5. The crystal holder64 includes an outer cylinder 66 of a material such as Lexan,manufactured by General Electric Co. This outer cylinder 66 receivesphenolic rod 67, which is a plastic consisting of pressed cellulosefiber that is considered a dead material as far as ultrasonic energy isconcerned.

The manner in which crystal 65 is positioned within the crystal holder64 is as follows. The phenolic rod 67 is milled from both ends toprovide a central seat portion 68 with a circumferential ledge 68". Thecrystal 65 which, in one actual embodiment'is a 2.25 megacycle crystalproduced by the Clevite Corp., is then bonded by epoxy resin to a nylonfocusing rod 69. at a flat end surface 69'. The rod 69 is then insertedinto the lower milled end of phenolic rod 67 until crystal 65 is seatedon ledge 68 and suitably secured therein as by epoxy. In this positioninternal lead wires 70 and 71, which are soldered to either side ofcrystal 65, can then be extended into the upper milled end of rod 67through small holes in the seat 68. Suitable external leads 70 and 71'are then connected to the internal lead wires, in the upper milled endand this end is then filled with epoxy as indicated at 72. Theseexternal leads are taken out through port 62 and thence through opening55 in the plate member 53.

The end face 69" of focusing rod 69 is then dressed so that it protrudesslightly from the holder 64 and will almost touch membrane 16 when theholder 64 is operatively positioned in the vertical position in the bodyportion 11.

Looking at FIG. 9 two crystals, 65, are shown, diagrammatically, assuitably coupled to the surface of a rail head 17. For ready referencethe crystal at the left is considered to be that associated with member43 while the crystal at the right is associated with the member 44 andits leads have prime indications. Leads 71 and 71' are to ground whilelead 72 is connected to contacts 73 and 74 of switches, generallyindicated at 75 and 76 respectively. Lead 72 is connected to contacts 77and 78 of the switches. As such switches are well known they are notillustrated in detail, but they can be mounted either on the analyzer oroutside this analyzer. For example, in FIG. 1, the switches 75 and 76are shown mounted on top wall portion 12 to be associated with thecrystals carried by the members 43 and 44 respectively.

In switch 75 the movable contact member 79 is connected to a transmittershown in block form at 80, while movable contact member 81 of switch 76is connected to a receiver shown in block form at 82. Transmitter 80 isconnected to a trigger (rep.rate) generator, shown by block 83 which inturn is connected to the gate shown by block 84. Gate 84 is connected tooscilloscope 85 and millivolt meter 86, both shown in block form.

Because the circuits for transmitter 80, receiver 82 trigger'(rep.rate)generator 83 and gate 84, are not, of themselves, a part of theinvention and because such circuits are well known in the art, it is notbelieved necessary to describe such circuits in detail.

For the moment it can be appreciated that when switches and 76 are inthe positions shown in FIG. 9, crystal 65 at the left can transmitultrasonic energy in a continuous mode to a lower surface of the railhead where it reflected to the crystal 65 at the right and the signal isdetected to be processed through the receiver 82 to the indicating meanssuch as the oscilloscope or the meter 86. Conversely, as the crystalscan be used interchangeably, contact 79 can be moved to engagement withcontact 75 and contact 81 be moved to engage contact 74, and then thetransmitting and receiving crystals are reversed.

On the other hand if the switch 76 is moved so that movable contactmember 81 engages switch contact 74 instead of contact 78 then thecrystal 65 on left continues to transmit but it is also connected to thereceiver 82 and the crystal 65 on the right is cut out of the circuit.In this arrangement crystal 65 at the left transmits energy and receivesenergy reflected at surface 17' in the known pulse-echo mode.

The mode of operation will be discussed in more detail later inconjunction with the use of the analyzer 10 to scan a transverse fissuredefect, generally shown at 87 in the rail head 17. Note that this defectextends vertically but, as is common with a defect of this type, it alsoextends an appreciable distance transversely of the rail head as seen inFIG. 10.

As illustrated in FIG. 9 the two crystals 65 are disposed at an anglewith respect to the top surface of the rail head 17 and means areprovided in the analyzer 10 whereby this angle can be varied to achieveoptimum and desired results. Attention is directed to FIGS. 1 and 5where a lever member 88 with a knob portion 89 is shown associated witheach of the crystal holder members 43 and 44. This lever member witheach of the members is disposed with the knob portion 89 over the topplate 45 and with the lever extending down through aligned slits 49, 41and 31 to be threadably engaged, at its lower end, in tapped opening 63of rod 61. As best seen in FIG. 5, lever member 88 extends throughopening 58 in tube 57 and it will be appreciated that by grasping knobportion 89 the lever member 88 can be swung to any desired positionalong scale 50 and this movement also swings the holder 64 with crystal65, in a vertical plane. As illustrated in FIGS. 3 and 5 the crystal 65is disposed at an angle of 30 with respect to the vertical, and this isindicated on scale 50.

The operation of analyzer 10 in conjunction with the electronic systemswill now be described. Assuming that a suspected defect in arailroadrail head or other parts of a rail has been located by other means, suchas a mobile flaw detector car passing along the track. The analyzer 10is then positioned on the top surface 13 of the rail head 17 with theindex mark 27' slightly to the left of the suspected defect. Indexmembers 23 on runners 22 are aligned with respect to the surface of therail head to define a longitudinal axis of scan selected according tothe probable location of the defect. For example, in the case of atypical detail fracture this axis would be chosen to be about half aninch from the gauge: side of the rail in track.

The sliding carriage 38 is centered in groove 29 as indicated alongscale 33. Crystal holder member 43 is located with the left edge of topplate 45, as viewed in FIG. 3, opposite the zero mark on scale 41'. Thecrystals 65 in both members 43 and 44 are moved, by

means of lever members 88, to an inclination angle of about 27 withrespect to the rail surface and as indicated along scale 50.

Movable contact member 79 of switch 75 is moved to contact 73 whilemovable contact member 81 of switch 76 is moved to contact 74 to enablethe crystal 65 in member 43 to transmit and receive in a pulseecho modeof operation.

After the preliminary work described above is completed the analyzer 10is moved from left to right until the defect is intercepted orencountered by the pulsedultrasonic energy wave train being transmittedby the crystal 65 and the ultrasonic energy is reflected to be receivedby this same crystal. This echoed signal appears on the screen of theoscilloscope 85 or, as an alternative, a simultaneous read-out, in theform of a sharp rise in voltage on the millivolt meter 86.

Movement of the analyzer 10 is continued toward the right until thesignal diminishes on the millivolt meter or the signal on the cathoderay tube of the oscilloscope migrates toward zero time or to apreselected grid line. This indicates transit of the defect and willlocate the defect within two or three inches of the zero point on scales26 and 33.

Next the members 43 and 44 are spaced apart on sliding carriage 38 aselected distance such as 4 inches. Now instead of a movement of theanalyzer 10 from left to right, as above described, the sliding carriage38 only is moved left to right until the signal is indicated anddiminishes, as also described above. The position of the index mark 51,on the member 43 with respect to scale 33 is noted when the signalmigrates to zero time or to the predetermined grid line on the scope.

Switches 75 and 76 are then reversed so that crystal 65 on member 44becomes the operative crystal in the pulse-echo mode of operation.Carriage 38 is then slid from right to left until the signal reflectedfrom the defect migrates to zero time or to a predetermined grid line,as above described. This position in scale 33 as indicated by index mark51, is noted and the central point on scale 33 between this position andthe position previously noted gives the approximate location of thedefect to be analyzed. The rail head 17 is marked at the correspondingpoint onscale 26 and the entire analyzer I is moved until the zero onscale.26 corresponds to the mark on the rail head. The analyzer is thencentered over the suspected defect which is to be analyzed in the mannerset forth below.

The analyzer 10 is now moved laterally on the surface of the rail head17 until the longitudinal axis of the crystals 65, which axis isindicated by index marks on end walls 15, is aligned at that position onthe surface marked at l as seen in FIG. 10. By means of knobs 24 thebody portion 1 1 can be inclined or canted on the runners 22magnetically clamped to the rail until a strong signal is reflected fromthe lower surface of 90 of the rail head'l7, as indicated by the dashedline extending from 1 to the arrow.

More or less simultaneously with the canting of the body portion 11 theangular disposition of the crystals 65 in the liquid in the boydportion, and with respect to the top surface 13 of the rail head 17, canbe adjusted by lever members 88 to achieve the best signal.

At this point movable contact member 79 of switch 75 is moved to contact73 while switch 76 is retained with movable contact member 81 andcontact 78 connected. This then enables the crystal 65 on member 43 fortransmission only while the other crystal on member 44 is for receivingonly.

The members 43 and 44 are then set on sliding carriage 38 at equaldistances away from the center (-1) mark on scale 41' and are clamped tothe carriage 38 by the permanent magnets 52 so they can move with thecarriage. The carriage 38 is then moved to the far left position, asseen in FIG. I, in groove 29 and a pass of the carriage to the right andalong position line 1 is commenced. It will be understood that, untilthe transmission of ultrasonic energy between the transmitting andreceiving crystals 65 is attenuated at the defect 87, the signal isreflected from the lower surface in the manner shown in FIG. 9.

Now assuming that the left and right hand crystals 65, shown in FIG. 9,are being moved to the right it will be apparent that the reflectedtrain of ultrasonic energy will ultimately impinge on a top surface 87'of defect 87 and transmission to the receiving crystal will be blockedfor a certain period of time during movement of the crystals to theright. Transmission will only be resumed as the train emerges from thedefect at the lower surface 87". This eclipse of ultrasonic energy isindicated by the oscilloscope 85 and millivolt meter 86 so that thelocation of the sliding carriage 38 can be determined at the time thetop surface 87' is encountered by the wave train and at the time thewave train emerges at the lower surface 87".

At the time the eclipse of ultrasonic energy commences a reading istaken with respect to the logarithmic and scalar grid 34. This involvesswinging marker arm 36, on pivot point 35, at the right until itencounters the magnetic lug stop member 48 on the holder member 44 towhich it will clamp. If, for example, the movable crystal holder members43 and 44 had been initially set at 2, as shown in FIG. 2, this scaleline on scale B is read to its intersection with marker arm 36 and givesthe depth of the upper limb or surface 87 in percentiles of thethickness of the material being tested, as read on the vertical lne ofscale A. In FIG. 2 it will be observed that at the dashed line positionof the marker arm 36 and at the 2.0 scale line of scale B, the 0 scaleline of scale A is read and this would indicate a percent depth or nodefect and a reflection from the lower surface .90.

The emergence of the train of ultrasonic energy from the lower limb orsurface 87" can be read in the same manner as described in the precedingparagraph.

After a pass has been made from left to right along the position line 1,as described above, and the appropriate readings taken, the slidingcarriage 38 can be moved to the far right position in groove 29 and apass made from right to left to take readings on the upper and lowerlimbs of the defect 87. In taking the readings in this direction it willbe understood that the marker arm 36 is moved to contact the magneticlug stop member 48 on the left hand member 43.

At this time two fixes have been obtained for depth of the upper andlower limbs of the defect 87 and it is possible'to average these to givea valid figure. However, if desired, additional fixes can be taken alongthe same position line 1 for corroboration. This can be done by spacingthe members 43 and 44 in the sliding carriage 38 at a different disianceand then repeating the passes and taking new reading on the logarithmicand scalar grid.

In order to determine the transverse extent of the defeet 87 it isnecessary to take passes along different position lines and a number ofsuch positions are illus- 'trated in FIG. 10. For example, aftercompletion of the passes along position line 1 the analyzer 10 can betransversely displaced so that the crystals are aligned at position 2and the same procedure of test can be repeated. This transversedisplacement of the analyzer can be repeated to any desired number ofpositions to determine the profile of the flaw.

While the discussion of the method of testing, according to theinvention, has so far been concerned with testing in the rail head 17the method is not limited to this area. As seen in FIG. 10, theultrasonic energy, being transmitted from transmitting crystal 65 to thereceiving crystal 65, can be reflected from the lower surface 90 of'therail head 17 as shown, for example, by dashed lines extending from 1 to5 and from 9 to 13. However, by canting the analyzer to a greater degreethe fillet area 91 can be scanned as indicated by the dashed lineextending from position 7.

The invention is also useful in testing in the web 92 of a rail. In thiscase the ultrasonic energy is reflected from'the lower surface 93 of thebase 94 of the rail. This is also shown in FIG. 10 by dashed linesextending from 6 to 8 into the web 92 and would be effective to locate adefect 95 which might be, for example, a bolt hole break.

After a number of fixes have been obtained it is desirable to record theresults on a plot sheet so that the extent of the flaw can be easilyseen and studied. This is important also as providing a record on whichsucceeding tests can be plotted to give a history of the material beingtested. In the case of welds this is particularly helpful because somewelds, such as welds in rail which are done in the field, present acomplex internal picture for analysis according to the invention. Thusthe keeping of comparative and continuing records of weld analysis isessential to any meaningful analysis of defective welds. in this respecta norm pattern can be established by the comparison and study of manytests of normal welds and important deviations established by visualinsepction through laboratory breakage While, as above described, it isdesirable that fixes on the flaw be taken from both sides of this flawit is not absolutely essential because it has been found that where thiscan not be done, as for example, a seamor some other impediment preventsa pass from one side, then fairly accurate fixes can be achieved fromthe other side only.

It will be understood that the above description of the presentinvention is susceptible to various modifictions, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

I claim:

1. A method for analyzing the extent of a defect, lying between spacedapart first and second boundary surfaces of a material, by means of apair of spaced apart ultrasonic transducers, which are???) nec tdto el ctiical s i giial g'eh eratiiig"and indicating means, and which aremovable as a unit over the first boundary surthe material at the firstboundary surface thereof, comprising the steps of:

a. moving the transducers spaced apart at a predetermaisiafieafiti it,along a first straight line lying over the firsrb un'd'i'r'y surface,toward the defect while simultaneously transmitting ultrasonic energyfrom one transducer, along a path of travel in which the energy isreflected from the second boundary surface, to the other transducerconnected to theindicating means;

b. moving a marker member to a position to indicate the location of oneof the transducers along the position line with respect to the locationof the defect when the indicating means shows that transmission ofultrasonic energy'along that portion of the path of travel from thesecond boundary surface to the other transducer is beginning to beattenuated at the defect;

c. reading a logarithmic and scalar grid associated with said markermember to determine the relative distance of the top of the defect fromthe first boundary surface as compared to the distance from that surfaceto the second boundary surface;

d. continuing the movement of the transducers as a unit along the firstposition line;

e. moving the marker member as in step (b) when the indicating meansshows that transmission of ultrasonic energy along the path of travelhas commenced again; and

f. reading the grid in the same manner as in step (c) Y but in order todetermine the relative position of the bottom of the defect.

2. The method as defined in claim 1 comprising the additional steps of:

g. reversing the connections from the electrical signal generating andindicating means to the transducers so that the flow of ultrasonicenergy along the path of travel is from the other transducer to the onetransducer;

h. moving the transducers as a unit along the first straight line towardthe defect but in the opposite direction to that of step (a); and

i. repeating steps (b) through (f).

3. The method as defined in claim 2, wherein steps (a) through (i) arerepeated along a second straight line transversely displaced from thefirst straight line but generally parallel thereto.

4. The method as defined in claim 2, wherein steps (a) through (i) aresuccessively repeated along a plurality of straight lines each of whichis transversely displaced from the first straight line but which aregenerally parallel thereto.

5. The method as defined in claim 1 wherein steps (a) through (f) arerepeated but with the transducers spaced apart at another predetermineddistance.

6. The method as defined in claim 2, wherein steps (a) through (i) arerepeated but with the transducers spaced apart at another predetrmineddistance.

face in ultrasonic ii'i y transmission relationship with 7. The methodas defined in claim 4 comprising the additional steps of plotting thedistance determinations obtained in steps (0) and (f).

1. A method for analyzing the extent of a defect, lying between spacedapart first and second boundary surfaces of a material, by means of apair of spaced apart ultrasonic transducers, which are connected toelectrical signal generating and indicating means, and which are movableas a unit over the first boundary surface in ultrasonic energytransmission relationship with the material at the first boundarysurface thereof, comprising the steps of: a. moving the transducersspaced apart at a predetermined distance and as a unit, along a firststraight line lying over the first boundary surface, toward the defectwhile simultaneously transmitting ultrasonic energy from one transducer,along a path of travel in which the energy is reflected from the secondboundary surface, to the other transducer connected to the indicatingmeans; b. moving a marker mEmber to a position to indicate the locationof one of the transducers along the position line with respect to thelocation of the defect when the indicating means shows that transmissionof ultrasonic energy along that portion of the path of travel from thesecond boundary surface to the other transducer is beginning to beattenuated at the defect; c. reading a logarithmic and scalar gridassociated with said marker member to determine the relative distance ofthe top of the defect from the first boundary surface as compared to thedistance from that surface to the second boundary surface; d. continuingthe movement of the transducers as a unit along the first position line;e. moving the marker member as in step (b) when the indicating meansshows that transmission of ultrasonic energy along the path of travelhas commenced again; and f. reading the grid in the same manner as instep (c) but in order to determine the relative position of the bottomof the defect.
 2. The method as defined in claim 1 comprising theadditional steps of: g. reversing the connections from the electricalsignal generating and indicating means to the transducers so that theflow of ultrasonic energy along the path of travel is from the othertransducer to the one transducer; h. moving the transducers as a unitalong the first straight line toward the defect but in the oppositedirection to that of step (a); and i. repeating steps (b) through (f).3. The method as defined in claim 2, wherein steps (a) through (i) arerepeated along a second straight line transversely displaced from thefirst straight line but generally parallel thereto.
 4. The method asdefined in claim 2, wherein steps (a) through (i) are successivelyrepeated along a plurality of straight lines each of which istransversely displaced from the first straight line but which aregenerally parallel thereto.
 5. The method as defined in claim 1 whereinsteps (a) through (f) are repeated but with the transducers spaced apartat another predetermined distance.
 6. The method as defined in claim 2,wherein steps (a) through (i) are repeated but with the transducersspaced apart at another predetermined distance.
 7. The method as definedin claim 4 comprising the additional steps of plotting the distancedeterminations obtained in steps (c) and (f).